exercise21_6barchart.java

java程序设计导论（daniel liang著） 所有偶数课后习题答案

import java.awt.*;
import javax.swing.JPanel;
import java.awt.event.*;

public class Exercise21_6BarChart extends JPanel implements ActionListener {
  BorderLayout borderLayout1 = new BorderLayout();
  Color[] colors = {Color.red, Color.yellow, Color.green, Color.blue,
    Color.cyan, Color.magenta, Color.orange, Color.pink,
    Color.darkGray};
  private Exercise21_6ChartModel model;

  public Exercise21_6BarChart() {
    this.setLayout(borderLayout1);
  }

  public void paintComponent(Graphics g) {
    super.paintComponent(g);

    if (model == null) return;

    String[] dataName = model.getDataName();
    double[] data = model.getData();

    // Find the maximum value in the data
    double max = data[0];
    for (int i=1; i<data.length; i++)
      max = Math.max(max, data[i]);

    int barWidth = (int)((getWidth() - 10.0) / data.length - 10);
    int maxBarHeight = getHeight() - 30;

    g.drawLine(5, getHeight() - 10, getWidth() - 5, getHeight() - 10);

    int x = 15;
    for (int i = 0; i < data.length; i++) {
      g.setColor(colors[i % colors.length]);
      int newHeight = (int)(maxBarHeight * data[i] / max);
      int y = getHeight() - 10 - newHeight;
      g.fillRect(x, y, barWidth, newHeight);
      g.setColor(Color.black);
      g.drawString(dataName[i], x, y - 7);
      x += barWidth + 10;
    }
  }

  public void setModel(Exercise21_6ChartModel newModel) {
    model = newModel;
    model.addActionListener(this);
  }

  public Exercise21_6ChartModel getModel() {
    return model;
  }

  public void actionPerformed(ActionEvent e) {
    repaint();
  }
}